The invention relates to a single-phase high voltage circuit-breaker comprising at least one interrupting chamber formed by an insulating tube filled with an insulation gas, and having, for at least one interrupting chamber, a current transformer which comprises a primary and a secondary. The secondary is disposed in air around the primary at one end of the tube, and the primary is at the high voltage electrical potential of the phase.
Patent document FR 2 525 807 discloses a high voltage circuit-breaker of that kind, in which the primary is constituted by a tubular conductor immersed in the insulation gas of the interrupting chamber. In an embodiment shown in FIG. 3 of that document, the secondary is based on a metal sleeve which surrounds the primary at one end of the insulating tube of the interrupting chamber. The sleeve is secured to a metal casing connected to ground potential and thus constitutes an electrostatic screen which enables the secondary to be at an electrical potential that is practically equal to ground potential. The current transformer implemented is of the xe2x80x9cconventionalxe2x80x9d type in that the winding wires of its secondary are practically at ground potential. Such a conventional current transformer suffers in particular from the drawback of requiring the winding wires of the secondary to be taken to measurement devices that are connected to ground, and this is generally performed by means of a metal tube protecting the wires and connecting the electrostatic screen to ground potential. This means in particular that a certain amount of ground area in the vicinity of the high voltage circuit-breaker is occupied.
Patent document DE 1 960 828.5 discloses a gas-insulated circuit-breaker with one or more current transformers of the xe2x80x9cincorporated electronicxe2x80x9d type, in which the secondary of the transformer is located in the insulation gas of the interrupting chamber at one end of the insulating tube that forms said chamber. Such a disposition has the advantage of being compact in terms of ground area occupancy, but suffers from the drawback of requiring transformer maintenance that can be expensive because of the difficulty in accessing the secondary of the transformer and the need under such circumstances to empty the insulation gas out from the circuit-breaker.
An object of the invention is to propose a circuit-breaker of the first kind as defined above that enables maintenance costs of the current transformer to be reduced and also reduces the ground area occupied by the circuit-breaker. Another object is to provide a current transformer arranged in modular manner so as to make to possible for the transformer to be mounted in a plurality of different configurations independently of the configuration of the circuit-breaker (column circuit-breaker or T-configuration).
To this end, the invention provides a circuit-breaker of the above-defined kind, wherein the primary is constituted by a metal annular support and wherein the secondary is subjected to a high voltage electrical potential that is practically equal to the potential of the primary.
The primary of the transformer is thus an annular electrical conductor surrounded by air, and the secondary surrounds the primary directly without any interposed electrostatic screen and without an element of the secondary being connected to ground potential.
The secondary can thus be associated with an optical or an optoelectronic circuit placed close thereto in air and subjected to the high voltage electrical potential, such a circuit being connectable to devices disposed on the ground by means of optical fibers. Transformer maintenance, e.g. changing optoelectronic circuit cards, is made easier because the secondary is disposed in air.
In addition to its electricity-conducting function, the primary of the transformer also performs a mechanical support function when it is disposed at the interface between the interrupting chamber of the circuit-breaker and a support column, or at the interface between the interrupting chamber of the circuit-breaker and a closure resistor casing, or else at the interface between the interrupting chamber of the circuit-breaker and an interconnection casing for connecting it to a support column in a T-configuration of circuit-breakers.
In an advantageous embodiment of a circuit-breaker of the invention, the annular support constituting the primary comprises an annular portion which includes an outer collar, said collar being in axial alignment with and being fixed to a metal flange that is electrically connected to a contact of the circuit-breaker. Nevertheless, this implementation is not the only way the primary can be connected to the high voltage electrical potential of the phase: it is possible to envisage an electrical connection between the support and the contact without requiring a metal flange, and the link element used need not necessarily be circularly symmetrical. In another embodiment, the annular support comprises another annular portion which engages coaxially and in gastight manner in the annular first portion. Nevertheless, there exist circuit-breaker configurations of the invention in which it is not necessary for a support to be made as two annular portions, for example when the diameter of the circuit-breaker support column is small compared with the diameter of the interrupting chamber. The annular support constituting the primary can then be constituted as a single annular portion of L-shaped radial section around which the secondary is engaged prior to assembling the interrupting chamber on the support column.
In a column circuit-breaker configuration or in a T-configuration of circuit-breakers, the measurement signals recovered by the opto-electronic circuit can be conveyed to the ground by optical fibers, the optical fibers advantageously being guided along the outside of the support column without using gastight feedthroughs. In particular, if the support column is constituted by a tube made of a composite material of the type comprising glass fibers embedded in resin and having an elastomer covering, the optical fibers are protected as from the time when the circuit-breaker mounted on the support column leaves the factory. When the circuit-breaker is in use, the optical fibers may also be guided to the ground inside an additional column insulator disposed parallel to the support column that supports the interrupting chamber of the circuit-breaker.